list: New SLIST_SPLICE() macro

6 files changed, 123 insertions, 5 deletions

diff --git a/build/prelude.mk b/build/prelude.mk
index d0968ea..38e432c 100644
--- a/build/prelude.mk
+++ b/build/prelude.mk
@@ -108,6 +108,7 @@ UNIT_OBJS := \
     obj/tests/bfstd.o \
     obj/tests/bit.o \
     obj/tests/ioq.o \
+    obj/tests/list.o \
     obj/tests/main.o \
     obj/tests/sighook.o \
     obj/tests/trie.o \
diff --git a/src/list.h b/src/list.h
index 61d0e5b..d95483f 100644
--- a/src/list.h
+++ b/src/list.h
@@ -324,6 +324,25 @@
 	LIST_VOID_(SLIST_INSERT_(list, &(list)->head, item, __VA_ARGS__))
 
 /**
+ * Splice a singly-linked list into another.
+ *
+ * @param dest
+ *         The destination list.
+ * @param cursor
+ *         A pointer to the item to splice after, e.g. &list->head or list->tail.
+ * @param src
+ *         The source list.
+ */
+#define SLIST_SPLICE(dest, cursor, src) \
+	LIST_VOID_(SLIST_SPLICE_((dest), (cursor), (src)))
+
+#define SLIST_SPLICE_(dest, cursor, src) \
+	*src->tail = *cursor, \
+	*cursor = src->head, \
+	dest->tail = *dest->tail ? src->tail : dest->tail, \
+	SLIST_INIT(src)
+
+/**
  * Add an entire singly-linked list to the tail of another.
  *
  * @param dest
@@ -332,10 +351,7 @@
  *         The source list.
  */
 #define SLIST_EXTEND(dest, src) \
-	SLIST_EXTEND_((dest), (src))
-
-#define SLIST_EXTEND_(dest, src) \
-	(src->head ? (*dest->tail = src->head, dest->tail = src->tail, SLIST_INIT(src)) : (void)0)
+	SLIST_SPLICE(dest, (dest)->tail, src)
 
 /**
  * Remove an item from a singly-linked list.
diff --git a/src/prelude.h b/src/prelude.h
index c4edcb2..0944df1 100644
--- a/src/prelude.h
+++ b/src/prelude.h
@@ -137,7 +137,7 @@ extern const char bfs_version[];
 /**
  * Get the length of an array.
  */
-#define countof(array) (sizeof(array) / sizeof(0[array]))
+#define countof(...) (sizeof(__VA_ARGS__) / sizeof(0[__VA_ARGS__]))
 
 /**
  * False sharing/destructive interference/largest cache line size.
diff --git a/tests/list.c b/tests/list.c
new file mode 100644
index 0000000..e14570f
--- /dev/null
+++ b/tests/list.c
@@ -0,0 +1,97 @@
+// Copyright © Tavian Barnes <tavianator@tavianator.com>
+// SPDX-License-Identifier: 0BSD
+
+#include "prelude.h"
+#include "tests.h"
+#include "list.h"
+
+struct item {
+	int n;
+	struct item *next;
+};
+
+struct list {
+	struct item *head;
+	struct item **tail;
+};
+
+static bool check_list_items(struct list *list, int *array, size_t size) {
+	struct item **cur = &list->head;
+	for (size_t i = 0; i < size; ++i) {
+		if (!bfs_check(*cur != NULL)) {
+			return false;
+		}
+		int n = (*cur)->n;
+		if (!bfs_check(n == array[i], "%d != %d", n, array[i])) {
+			return false;
+		}
+		cur = &(*cur)->next;
+	}
+
+	if (!bfs_check(*cur == NULL)) {
+		return false;
+	}
+	if (!bfs_check(list->tail == cur)) {
+		return false;
+	}
+
+	return true;
+}
+
+#define ARRAY(...) (int[]){ __VA_ARGS__ }, countof((int[]){ __VA_ARGS__ })
+#define EMPTY() NULL, 0
+
+bool check_list(void) {
+	struct list l1;
+	SLIST_INIT(&l1);
+	bfs_verify(check_list_items(&l1, EMPTY()));
+
+	struct list l2;
+	SLIST_INIT(&l2);
+	bfs_verify(check_list_items(&l2, EMPTY()));
+
+	SLIST_EXTEND(&l1, &l2);
+	bfs_verify(check_list_items(&l1, EMPTY()));
+
+	struct item i10 = { .n = 10 };
+	SLIST_APPEND(&l1, &i10);
+	bfs_verify(check_list_items(&l1, ARRAY(10)));
+
+	SLIST_EXTEND(&l1, &l2);
+	bfs_verify(check_list_items(&l1, ARRAY(10)));
+
+	SLIST_SPLICE(&l1, &l1.head, &l2);
+	bfs_verify(check_list_items(&l1, ARRAY(10)));
+
+	struct item i20 = { .n = 20 };
+	SLIST_PREPEND(&l2, &i20);
+	bfs_verify(check_list_items(&l2, ARRAY(20)));
+
+	SLIST_EXTEND(&l1, &l2);
+	bfs_verify(check_list_items(&l1, ARRAY(10, 20)));
+	bfs_verify(check_list_items(&l2, EMPTY()));
+
+	struct item i15 = { .n = 15 };
+	SLIST_APPEND(&l2, &i15);
+	SLIST_SPLICE(&l1, &i10.next, &l2);
+	bfs_verify(check_list_items(&l1, ARRAY(10, 15, 20)));
+	bfs_verify(check_list_items(&l2, EMPTY()));
+
+	SLIST_EXTEND(&l1, &l2);
+	bfs_verify(check_list_items(&l1, ARRAY(10, 15, 20)));
+
+	SLIST_SPLICE(&l1, &i10.next, &l2);
+	bfs_verify(check_list_items(&l1, ARRAY(10, 15, 20)));
+
+	SLIST_SPLICE(&l1, &l1.head, &l2);
+	bfs_verify(check_list_items(&l1, ARRAY(10, 15, 20)));
+
+	struct item i11 = { .n = 11 };
+	struct item i12 = { .n = 12 };
+	SLIST_APPEND(&l2, &i11);
+	SLIST_APPEND(&l2, &i12);
+	SLIST_SPLICE(&l1, &l1.head->next, &l2);
+	bfs_verify(check_list_items(&l1, ARRAY(10, 11, 12, 15, 20)));
+
+	return true;
+}
diff --git a/tests/main.c b/tests/main.c
index aef0583..bef2e37 100644
--- a/tests/main.c
+++ b/tests/main.c
@@ -111,6 +111,7 @@ int main(int argc, char *argv[]) {
 	run_test(&ctx, "bfstd", check_bfstd);
 	run_test(&ctx, "bit", check_bit);
 	run_test(&ctx, "ioq", check_ioq);
+	run_test(&ctx, "list", check_list);
 	run_test(&ctx, "sighook", check_sighook);
 	run_test(&ctx, "trie", check_trie);
 	run_test(&ctx, "xspawn", check_xspawn);
diff --git a/tests/tests.h b/tests/tests.h
index de95a49..2958fe1 100644
--- a/tests/tests.h
+++ b/tests/tests.h
@@ -27,6 +27,9 @@ bool check_bit(void);
 /** I/O queue tests. */
 bool check_ioq(void);
 
+/** Linked list tests. */
+bool check_list(void);
+
 /** Signal hook tests. */
 bool check_sighook(void);